Hi again,
I've already asked this question to Nick but as he said, this is not possible because the schedules have different layouts.
The resources can only belong to one schedule

.
Perhaps you could create only one schedule named "Event" and set the access to the 3 rooms according to the type of event the user is allowed to reserve (Application Management > Users >Permissions).
Or perhaps you could use the possibility to add a new field in the reservation page (v2.1.4) and ask the users to specify which type of event will occur in the romm they are booking.
BR